1. Field of the Invention
The present invention relates generally to a wiper control system for an automotive vehicle, which wiper control system is facilitated with an INTERMITTENT mode operation. More specifically, the invention relates to an automotive wiper control system with a fail-safe feature to avoid burnout of a wiper motor even when a wiper blade assembly is stuck or locked on the vehicular windshield. Further particularly, the invention relates to an automotive wiper control system with an auto-stop function for automatically stopping the wiper blade assembly at a predetermined position and a fail-safe function cooperating with the auto-stop function.
2. Description of the Prior Art
It is usually experienced that a wiper blade assembly of an automotive wiper system locks due to substantial resistance against the wiper blade. For example, it is frequently experienced that the wiper blade is locked at an intermediate position between its motion ends during driving of the vehicle in the snow. When such high resistance is exerted to lock the wiper blade, driving power tends to be applied to the wiper motor to cause it to burn out. In order to prevent the wiper motor from burning out, there has been proposed, in the conventional wiper system, to provide a circuit breaker which is responsive to an internal temperature of the wiper motor to break power supply for the wiper motor when the internal temperature of the wiper motor becomes excessive. In the usual case, such a circuit breaker is successful to prevent the wiper motor from burning out by breaking power supply everytime the internal temperature of the wiper motor becomes excessive. Such type of wiper systems have been disclosed in the Japanese Patent Second Publication (Tokko) Showa 60-52013 and the Japanese Utility Model Second Publication (Jikko) Showa 44-17930.
However, such wiper systems with circuit breakers will not be successful in prevention of burn-out of the wiper motors in substantially cold environmental conditions. For instance, when the atmospheric temperature is approximately -40.degree. C., the internal temperature of the wiper motor will not rise to the given temperature at which the circuit breaker becomes active. Therefore, the power supply can be continued until burnout of the wiper motor occurs.